CTM refund policy a ****

I purchased tiles and peripherals from CTM on black Friday totaling over R9000 . Two weeks later I returned most of the items as I did not need it. The calculated refund was R8450 and was confirmed by the assistant Mike. The refund was made within 7 days, but the value was R7595. When I spoke to a senior staff member at the Southgate branch of CTM, Mary, she said that the refund was smaller due to black Friday. I'm fully in awe. Can someone please help me.